JPH0492533A - Medium access method for loop type lan - Google Patents

Abstract

PURPOSE:To attain an access to a medium with high reliability and at a low cost by connecting together the medium attachment units MAU connected to the terminals in a loop form and cutting a signal line at each junction in a medium access state in order to secure an open loop form for the connection state. CONSTITUTION:The MAU 41-52 connected to the terminals 21-32 are connected together in a loop form, and a loop cutting control circuit 21f and a loop cutting circuit 21b are provided to each MAU in order to internally cut a signal line in the transmission states of the terminals 21-32. In a medium access state, the signal line is cut at the junction of the terminal where an access is applied so that the connection state is changed to an open loop form. The circuit 21b cuts the signal line at the loop junction of a relevant MAU to secure an open loop state and prevents the transmission of the signal of another terminal to the destination terminal of transmission. Thus the loop connection in secured for a LAN of a CSMA/CD transmission control system and an inexpensive and highly reliable access is attained to a medium.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a medium access method in a C3MA/CD type LAN, and particularly relates to a medium access method in a C3MA/CD type LAN.
This invention relates to an AN medium access method.

[Prior Art] As a conventional medium access method in LAN, C3
There was MA and token passing methods.

For example, C3MA/CD of IEEE802.3 standard (
carrier 5ense multiple
access/collision detection
In method n), if the terminal monitors the signal on the medium and is detecting the signal, the bit string constituting the transmission data is being transmitted through the medium, so transmission is postponed. Further, if there is no signal, the transmission is performed, and if a collision is detected, the transmission is interrupted, and after waiting for a predetermined time, the transmission is retransmitted.

In addition, the token hash method of the IEEE802.4 standard and the
In the token hash system of the EEE802.5 standard, special packets called tokens flow on the media, and a transmitting terminal gains the right to transmit when a token arrives at its own device.

Regarding conventional LAN, for example, "TLf Information and Communication Handbook, IEICE Line (1988), p.
p. 2658-2673''.

“Problem to be solved by the invention” In the above-mentioned conventional technology, the IE
When using the C3MA/CD method of the EE802.3 standard, for example, if collision detection is performed in an analog manner as in the 108ASE5 of the IEE and E802.3 standards, there is an aspect of uncertainty; IBASE5
If done digitally, separate equipment would be required and expensive.

In addition, IEEE802 is suitable for relatively large systems.
．． When using the token ring method of the 5 standard, there is relatively little decrease in throughput even if the number of transmitting terminals increases, but it becomes expensive due to token management and the like.

SUMMARY OF THE INVENTION An object of the present invention is to solve these problems and provide a medium access method for a loop-type LAN that is inexpensive and highly reliable.

[Means for Solving the Problems] In order to achieve the above object, the loop-type LAN medium access method of the present invention provides an M A v (Medium At
tachment Lin1t) in a loop,
The MAU is equipped with a means (loop disconnection control circuit, loop disconnection circuit) for internally disconnecting the signal line when the terminal is transmitting, and when accessing the medium, the signal line is disconnected at the connection point of the accessing terminal and the connection configuration is changed. The feature is that it is in an open loop state.

[Operation] In the present invention, when a transmission signal is input from the terminal through the transmission signal MALI/terminal 1/F of the MAU during medium access, the loop disconnection control circuit sends a loop disconnection signal to the loop disconnection circuit.

Then, the loop cutting circuit cuts the signal line at the loop connection point of that MAtJ, creating an open loop state and preventing signals from other terminals from being sent to the destination terminal.

As a result, the LAN of the C3MA/CD transmission control method
can be connected in a loop to provide inexpensive and reliable medium access.

[Example] An embodiment of the present invention will be described below with reference to the drawings.

FIG. 2 is a configuration diagram of a loop type LAN in one embodiment of the present invention.

In Fig. 2, 21 to 32 are terminals (A) to terminals (L).
, 41 to 52 are M A U (A) to M A U (L
).

Further, the MAUs 41 to 52 sequentially connect media in a loop, and each MAU is connected to a terminal to exchange data. In this case, transmission control is performed using the C3MA/CD method, and the signals circulate in directions (A) to (L).

Here, the configuration and functions of the MAU will be described in detail.

FIG. 3 is a configuration diagram of M AU (A) in FIG. 2.

In FIG. 3, 21a is a receiver, 21b is a loop cutting circuit that cuts the signal line when sending a signal in response to a loop cutting signal from the loop cutting control circuit 21f, 21c is a retiming circuit, 21d is a driver, and 2]e is a terminal. (l,
) 32 to the terminal (A) 21/terminal T/F, 2]f is the loop cutting circuit 21b
21g is a transmission signal MAU/terminal]/F which inputs a signal from the terminal (A) 2+.

Next, the medium access procedure of this embodiment will be described.

FIG. 1 is a flowchart showing a medium access method in one embodiment of the present invention.

In this embodiment, when a terminal transmits a signal, the MAU connected to the terminal confirms that no signal is being transmitted from another terminal on the media (101), and transmits data to the other terminal (102). ).

At the same time, the MALJ internally disconnects the signal line on the opposite side from the other terminal to create an open loop state (103).

After that, when the signal transmitted by that terminal circulates around the loop-connected media and returns, the MAU takes it in, and the terminal checks whether the signal and the transmitted data match (105). , if they match, the process ends normally (
+07). If the data does not match, it is determined that a collision has occurred, and the data is discarded and sent again (+
06).

Next, a specific example will be explained with reference to FIGS. 2 and 3.

For example, when terminal (A) 21 transmits to terminal (G) 27, MAtJ (A) 41 looks at the media on the 1MAtJ (L) 52 side, confirms that the signal is not ON, and then
l(B) Sends the signal to the media on the 42 side.

This transmission data is the transmission signal MAU/terminal 1/F21g
The signal is input to the loop cutting control circuit 21f through the driver 21 (l) and sent to the MAU (B) 42 through the driver 21 (l).

On the other hand, due to the transmitted data, the loop disconnection control circuit 21
A loop disconnection signal is output from f, and the loop disconnection circuit 2
1b operates, MAU (L) 52 to MAU (B) 42
The signal line going to is cut off on the MAU(L) 52 side. That is, the signal from MALI (L) 52 is M, AU
(B) I won't go to 42.

Note that if there is no data to be transmitted, the signal from the MAIJ(L) 52 passes through the loop cutting circuit 21b as it is, is regenerated and amplified by the retiming circuit 21c, and is sent to the driver 2+c.
1 to MAU (B) 42.

In this way, the signal transmitted from MAU (A) 41 is
When it passes through MAU (G) 47, it enters terminal (G) 27, and since the addresses match, it is taken in. Then, it goes around the loop and returns to MAU (A) 41, and terminal (A) 2
1.

At this time, the data is checked, and if it matches the transmitted data, it is determined that the data has been transmitted and received normally. Also, what if they don't match? # It is suddenly judged. In addition, M.A.
The signal from the U(L) 52 is sent to the terminal (A) 21 through the receiver reception signal MA/terminal 1/F 21e, whether it is being transmitted or not, and the data is checked there. At times other than when sending data, it is determined whether the data is addressed to the user based on the destination address of the data, and if the data is addressed to the user, the data is captured.

For example, terminal (D) 24 also tries to transmit at the same time as terminal (A) 2], and MAU (D), +4 is transmitted to MAU (C) 43.
If the MAIJ (D) 44 looks at the media on the side and confirms that the signal is not ON, it transmits the signal to the media on the MAIj (E) 45 side, and at the same time sends the signal to the media on the MAIj (C) 43
, the signal line between MAU(E) 45 and MAU(C) 43
The signal from 1MAU (C)43 is disconnected at the side.
11(E) Avoid going to the 4.5 side.

In this case, when a signal comes from the MAU (A) 41, it passes through the MAU (D) 44 and enters the terminal (D) 24, but at the terminal (D) 24, it collides because it does not match the transmitted data. It is determined that this has occurred and the data is discarded. Thereafter, retransmission is performed, but since the addresses of the sending terminals of the colliding data are included in the mutually returned data, it is easy to determine which one should be returned with priority.

In addition, in this example, 12 terminals are connected, but
There is no limit to the number of devices, and similarly inexpensive and highly reliable medium access can be performed.

〔effect〕

According to the present invention, in the LAN device, C5>IA/C
Since the transmission control method of D is implemented using a loop-like connection method, collision detection is simple and reliable, and an inexpensive and highly reliable system can be realized.

[Brief explanation of drawings]

FIG. 1 is a flowchart showing a medium access method in an embodiment of the present invention, FIG. 2 is a configuration diagram of a loop type LAN in an embodiment of the present invention, and FIG. 3 is a flowchart showing a medium access method in an embodiment of the present invention.
It is a block diagram of Ll (A). 21 to 32: Terminal (A) to terminal (L), 2]a: Receiver, 21b/loop cutting circuit, 21c retiming circuit, 21d driver, 21e: Received signal MAU/terminal I/F, 21f: loop cutting control circuit. 21g Transmission signal MAU/terminal 1/F, 41-52
・MA tJ (A) ~ MAU (L). Figure Figure

Claims (1)

[Claims] (1) In a CSMA/CD type LAN medium access method, MAUs connected to terminals are connected in a loop, and each MAU is provided with a means for internally cutting the signal line when the terminal is transmitting, and medium access is A medium access method for a loop-type LAN, which is characterized in that the signal line is sometimes cut at the connection point of the accessing terminal to create an open loop connection.